JP6365601B2 - Magnetic marker detection system and magnetic marker detection method - Google Patents

Description

  The present invention relates to a magnetic marker detection system and a magnetic marker detection method for detecting a magnetic marker laid on a road.

  Conventionally, a magnetic marker detection system for a vehicle for using a magnetic marker laid on a road for vehicle control is known (see, for example, Patent Document 1). If such a magnetic marker detection system can detect, for example, a magnetic marker laid along a lane with a vehicle magnetic sensor or the like, various driving assistance such as automatic steering control, lane departure warning, and automatic driving can be realized. .

JP 2005-202478 A

  However, the conventional magnetic marker detection system has the following problems. That is, there is a problem that the certainty of detection of the magnetic marker may be impaired due to various disturbance magnetism acting on the magnetic sensor or the like. For example, a side-by-side vehicle or a passing vehicle can be a source of disturbance magnetism.

  The present invention has been made in view of the above-described conventional problems, and aims to provide a magnetic marker detection system and a magnetic marker detection method with high detection reliability.

One aspect of the present invention is a magnetic marker detection system that detects a magnetic marker disposed on a travel path using marker detection means provided in at least two locations separated in the front-rear direction of the vehicle.
Determination to determine whether or not a magnetic marker has been detected based on at least one of the detection result of the magnetic marker by the front marker detection means and the detection result of the magnetic marker by the rear marker detection means Having means,
In the determination means, the other marker detection means detects the same magnetic marker within a predetermined period based on the time point when one of the front and rear marker detection means detects the magnetic marker, The magnetic marker detection system is set as a condition for confirming the determination that the magnetic marker has been detected.

One aspect of the present invention is a magnetic marker detection method for detecting a magnetic marker disposed on a travel path using marker detection means provided at least at two locations separated in the longitudinal direction of a vehicle.
A first detection step of performing magnetic marker detection processing by the front marker detection means;
When a magnetic marker is detected by the front marker detection means, a time point at which the rear marker detection means can detect the same magnetic marker is predicted based on the time point of the detection, and a predetermined period including the time point at which the detection is possible is determined. A period setting step to be set;
The magnetic marker detection method includes a second detection step of executing a magnetic marker detection process by the rear marker detection means during the predetermined period set in the period setting step.

  The magnetic marker detection system according to the present invention is a system that improves the detection accuracy of a magnetic marker by using marker detection means disposed at least at two locations separated in the front-rear direction of the vehicle. In this magnetic marker detection system, the other marker detection means detects the same magnetic marker within a predetermined period based on the time when one of the front and rear marker detection means detects the magnetic marker. Is set as a condition for deterministic detection of the magnetic marker. Therefore, even if erroneous detection occurs in the front marker detection means and the rear marker detection means, an erroneous determination that a magnetic marker has been detected is not immediately established.

  In the magnetic marker detection method according to the present invention, the rear marker detection means executes a magnetic marker detection process in a predetermined period set according to the detection of the magnetic marker by the front marker detection means. Therefore, even if an erroneous detection occurs in the front marker detection means, the erroneous detection is not immediately confirmed. Further, since the rear marker detection means executes detection processing when a magnetic marker is detected by the front marker detection means, the possibility of erroneous detection is low. Even if the front magnetic sensor generates a false detection, if the back magnetic sensor does not detect a magnetic marker in the predetermined period set in response to the false detection, It can be determined that the detection result of the front magnetic sensor is wrong or the reliability is low.

  Thus, the magnetic marker detection system and magnetic marker detection method according to the present invention are systems or methods for detecting magnetic markers with high certainty.

The front view which looks at the vehicle which attached the sensor unit in Example 1. FIG. 1 is a configuration diagram of a magnetic marker detection system in Embodiment 1. FIG. 1 is a block diagram showing an electrical configuration of a magnetic marker detection system in Embodiment 1. FIG. FIG. 3 is a block diagram illustrating a configuration of a magnetic sensor in the first embodiment. FIG. 3 is an explanatory diagram illustrating temporal changes in the magnetic distribution in the vehicle width direction when passing through a magnetic marker in the first embodiment. FIG. 3 is an explanatory diagram illustrating a temporal change in a peak value of a magnetic measurement value when passing through a magnetic marker in the first embodiment. FIG. 3 is a flowchart showing a flow of processing by the magnetic marker detection system in the first embodiment. Explanatory drawing of the detection period by the back side sensor unit in Example 1. FIG. Explanatory drawing which illustrates the time change of the magnetic gradient of the vehicle width direction at the time of passing the magnetic marker in Example 1. FIG. FIG. 9 is a flowchart showing a flow of processing by the magnetic marker detection system in the second embodiment. Explanatory drawing of the predetermined period in Example 2. FIG.

A preferred embodiment in the present invention will be described.
In the magnetic marker detection system of the present invention, as a condition for confirming the determination that the magnetic marker has been detected, the time point when one of the front and rear marker detection means detects the magnetic marker is used. It is set that the other marker detection means detects the same magnetic marker within a predetermined period as a reference. The predetermined period differs depending on which of the one marker detection means is a past period or a future period with respect to the reference time point. When the one marker detection means is a front marker detection means, the predetermined period is a future period with respect to the reference time point, while in the rear case, it is a past period.

In the magnetic marker detection system of the present invention, when the front marker detection unit detects a magnetic marker, the time period including the time point at which the rear marker detection unit is predicted to detect the same magnetic marker is A system having period setting means for setting as a predetermined period is preferable.
In this case, when the front marker detection means detects the magnetic marker, the front marker detection means determines whether or not the rear marker detection means has detected the same magnetic marker in the predetermined period. The correctness of detection can be confirmed.

The rear marker detection means may execute a magnetic marker detection process in the predetermined period.
In this case, it is possible to efficiently confirm whether the detection by the front marker detection means is correct or not by executing detection processing by the rear marker detection means during the predetermined period.

In the magnetic marker detection system of the present invention, any one of the front and rear marker detection means alternatively executes a magnetic marker detection process,
During the predetermined period, the rear marker detection means executes detection processing, while during the other operation periods, the front marker detection means preferably executes detection processing.

  When either one of the front side and rear side marker detection means alternatively executes the magnetic marker detection process, it is possible to suppress the calculation processing load on the entire system. Further, if it is not necessary to execute the detection processes in parallel, the hardware can be configured on a small scale, and the hardware cost can be suppressed.

The length of the predetermined period is different depending on the vehicle speed, which is the speed of the vehicle, and the predetermined period is preferably shorter as the vehicle speed is higher.
If the detection range of the marker detection means is constant, the time required for the magnetic marker to pass through the detection range becomes shorter as the vehicle speed increases. If the predetermined period is constant regardless of the vehicle speed, the ratio of the time during which the magnetic marker is located in the detection range of the marker detection means and can be detected in the predetermined period depends on the vehicle speed. Change. The higher the vehicle speed, the lower this ratio and the higher the possibility of erroneous detection.

  Therefore, if the predetermined period is shortened as the vehicle speed increases as described above, the ratio of the time during which the magnetic marker is located in the detection range of the marker detection means in the predetermined period can be increased. As a result, the number of times the detection process is attempted can be reduced in spite of the fact that the magnetic marker is not located within the detection range, and erroneous detection can be avoided in advance.

The marker detection means can detect the amount of lateral deviation of the vehicle relative to the magnetic marker,
The index value for the determination means to confirm the determination includes a difference between the first lateral deviation amount detected by the front marker detection means and the second lateral deviation amount detected by the rear marker detection means. It is preferable that the fluctuation amount is included (claim 6).

  In this case, erroneous detection can be found depending on whether or not the fluctuation amount of the lateral deviation amount when the vehicle passes the magnetic marker is appropriate. For example, even when both the front marker detection unit and the rear marker detection unit detect a magnetic marker, if the lateral deviation is excessive, it is determined that the magnetic marker has been detected. It is possible to determine that the reliability is not high or the detection is false.

In the magnetic marker detection method according to the present invention, the first detection step may be repeatedly executed until the magnetic marker is detected by the front marker detection means.
In this case, it is not necessary to wastefully execute the period setting step and the second detection step, and hardware resources can be used efficiently.

The embodiment of the present invention will be specifically described with reference to the following examples.
Example 1
This example is an example relating to a magnetic marker detection method and a magnetic marker detection system 1 for detecting a magnetic marker 10 laid on a road. The contents will be described with reference to FIGS.

  The magnetic marker detection system 1 is a vehicle-side system for detecting a magnetic marker 10 laid on a road (running road) as shown in FIGS. 1 to 3, and a magnetic sensor Cn (n is an integer of 1 to 15). ) Including a sensor unit (marker detection means) 11 and a detection unit 12 that controls the sensor unit 11. Hereinafter, after the magnetic marker 10 is outlined, the sensor unit 11 and the detection unit 12 that constitute the magnetic marker detection system 1 will be described.

The magnetic marker 10 is a road marker laid on the road surface 100S along the center of the lane 100 in which the vehicle 5 travels. The magnetic marker 10 has a columnar shape with a diameter of 20 mm and a height of 28 mm, and can be accommodated in a hole provided in the road surface 100S. The magnet constituting the magnetic marker 10 is a ferrite plastic magnet in which magnetic powder of iron oxide, which is a magnetic material, is dispersed in a polymer material, which is a base material, and has a characteristic of maximum energy product (BHmax) = 6.4 kJ / m ^3. It has. The magnetic marker 10 is laid while being accommodated in a hole formed in the road surface 100S.

この磁気マーカ１０は、磁気センサＣｎの取付け高さとして想定する範囲１００〜２５０ｍｍの上限の２５０ｍｍ高さにおいて、８μＴ（８×１０^−６Ｔ）の磁束密度の磁気を作用できる。 A part of the specification of the magnetic marker 10 of this example is shown in Table 1.

The magnetic marker 10 can act with a magnetism having a magnetic flux density of 8 μT (8 × 10 ⁻⁶ T) at an upper limit of 250 mm, which is an upper limit of a range of 100 to 250 mm assumed as a mounting height of the magnetic sensor Cn.

Next, the sensor unit 11 and the detection unit 12 constituting the magnetic marker detection system 1 will be described.
As shown in FIGS. 1 and 2, the sensor unit 11 is a unit attached to a vehicle body floor 50 that hits the bottom surface of the vehicle 5. In the magnetic marker detection system 1, sensor units 11 are arranged at two spaced locations in the front-rear direction of the vehicle 5. In the following description, the interval between the front sensor unit 11 and the rear sensor unit 11 in the front-rear direction of the vehicle is referred to as a sensor span S.

The front sensor unit 11 is attached near the inside of the front bumper, and the rear sensor unit 11 is attached near the inside of the rear bumper. In the case of the vehicle 5 of this example, the mounting height with respect to the road surface 100S is 200 mm.
As shown in FIGS. 2 and 3, each sensor unit 11 includes 15 magnetic sensors Cn arranged in a straight line along the vehicle width direction, and a detection processing circuit 110 incorporating a CPU (not shown). Yes.

  The detection processing circuit 110 (FIG. 3) is an arithmetic circuit that executes various arithmetic processes such as a marker detection process (detection process) for detecting the magnetic marker 10. The detection processing circuit 110 is configured by using an element such as a ROM (read only memory) or a RAM (random access memory), in addition to a CPU (central processing unit) that executes various operations. .

  The detection processing circuit 110 acquires a sensor signal output from each magnetic sensor Cn and executes marker detection processing and the like. All detection results of the magnetic marker 10 calculated by the detection processing circuit 110 are input to the detection unit 12. Note that both the front and rear sensor units 11 can execute marker detection processing at a cycle of 3 kHz.

  Here, the configuration of the magnetic sensor Cn will be described. In this example, a one-chip MI sensor in which the MI element 21 and the drive circuit are integrated is employed as the magnetic sensor Cn (see FIG. 4). The MI element 21 is an element including an amorphous wire 211 made of a CoFeSiB alloy and having substantially zero magnetostriction, and a pickup coil 213 wound around the amorphous wire 211. The magnetic sensor Cn detects magnetism acting on the amorphous wire 211 by measuring a voltage generated in the pickup coil 213 when a pulse current is applied to the amorphous wire 211. The MI element 21 has detection sensitivity in the axial direction of the amorphous wire 211 that is a magnetic sensitive body. In each magnetic sensor Cn of the sensor unit 11 of this example, an amorphous wire 211 is disposed along the vertical direction.

  The drive circuit is an electronic circuit including a pulse circuit 23 that supplies a pulse current to the amorphous wire 211 and a signal processing circuit 25 that samples and outputs a voltage generated in the pickup coil 213 at a predetermined timing. The pulse circuit 23 is a circuit including a pulse generator 231 that generates a pulse signal that is a source of a pulse current. The signal processing circuit 25 is a circuit that takes out an induced voltage of the pickup coil 213 through a synchronous detection 251 that is opened and closed in conjunction with a pulse signal, and amplifies it with a predetermined amplification factor by an amplifier 253. The signal amplified by the signal processing circuit 25 is output to the outside as a sensor signal.

  The magnetic sensor Cn is a highly sensitive sensor having a magnetic flux density measurement range of ± 0.6 millitesla and a magnetic flux resolution within the measurement range of 0.02 microtesla. Such high sensitivity is realized by the MI element 21 utilizing the MI effect that the impedance of the amorphous wire 211 changes sensitively according to the external magnetic field. Further, the magnetic sensor Cn can perform high-speed sampling at a cycle of 3 kHz, and is compatible with high-speed driving of the vehicle. In this example, the period of magnetic measurement by the sensor unit 11 is set to 3 kHz, and the sensor unit 11 inputs a sensor signal to the detection unit 12 every time the magnetic measurement is performed.

Table 2 shows a part of the specifications of the magnetic sensor Cn.

As described above, the magnetic marker 10 can act with magnetism having a magnetic flux density of 8 μT (8 × 10 ⁻⁶ T) or more in the range of 100 to 250 mm assumed as the mounting height of the magnetic sensor Cn. If the magnetic marker 10 acts on magnetism having a magnetic flux density of 8 μT or more, it can be detected with high reliability using the magnetic sensor Cn having a magnetic flux resolution of 0.02 μT.

  As shown in FIGS. 1 to 3, the detection unit 12 controls the front and rear sensor units 11, and uses the detection results of each sensor unit 11 to determine and output the final detection results. is there. In addition to the front and rear sensor units 11, a vehicle speed sensor, a vehicle ECU, and the like are electrically connected to the detection unit 12. The detection result output from the detection unit 12 is input to a vehicle ECU (not shown) and is used for various types of control on the vehicle side, such as automatic steering control for maintaining a lane, lane departure warning, and automatic driving.

  The detection unit 12 is a unit including an electronic substrate (not shown) on which a memory element such as a ROM or a RAM is mounted in addition to a CPU that executes various calculations. The detection unit 12 controls the operation of the front sensor unit 11 and the rear sensor unit 11, and integrates the detection results of the sensor units 11 to determine and output a final detection result.

The detection unit 12 has functions as the following means.
(A) Determining means: Determines whether or not the magnetic marker 10 has been detected based on at least one of the detection result by the front sensor unit 11 and the detection result by the rear sensor unit 11. means.
(B) Period setting means: when the front sensor unit 11 detects the magnetic marker 10, predicts a time point at which the rear sensor unit 11 can detect the same magnetic marker 10, and a time period including the detectable time point Means for setting as a detection period (predetermined period).

Next, (1) marker detection processing for each sensor unit 11 to detect the magnetic marker 10 will be described, and then (2) the overall operation flow of the magnetic marker detection system 1 will be described.
(1) Marker detection processing The sensor units 11 on the front side and the rear side perform marker detection processing at a period of 3 kHz in a later-described period designated by the detection unit 12. The sensor unit 11 obtains a magnetic distribution in the vehicle width direction by sampling the magnetic measurement values represented by the sensor signals of the 15 magnetic sensors Cn at each execution period (p1 to p7) of the marker detection process (see FIG. 5). ). The peak value of the magnetic distribution in the vehicle width direction becomes maximum when passing through the magnetic marker 10 as shown in the figure (period p4 in FIG. 5).

  When the vehicle 5 travels along the lane 100 on which the magnetic marker 10 is laid, the peak value of the magnetic distribution in the vehicle width direction increases every time it passes through the magnetic marker 10 as shown in FIG. In the marker detection process, a threshold value determination regarding this peak value is executed, and it is determined that the magnetic marker 10 has been detected when it is equal to or greater than a predetermined threshold value.

  When the sensor unit 11 detects the magnetic marker 10, the sensor unit 11 identifies which magnetic sensor Cn has a peak magnetic measurement value. Then, the positional deviation amount in the vehicle width direction of the specified magnetic sensor with respect to the center of the sensor unit 11 is detected as the lateral deviation amount of the vehicle 5 with respect to the magnetic marker 10. If the magnetic distribution in the vehicle width direction is approximated by a curve and the position of the peak value is specified with an accuracy finer than the interval between the 15 magnetic sensors, the accuracy of the lateral deviation can be further improved.

(2) Overall Operation of Magnetic Marker Detection System 1 The overall operation of the magnetic marker detection system 1 will be described with reference to the flowchart of FIG.
The detection unit 12 causes the front sensor unit 11 to execute the marker detection process (S101, first detection step), and repeatedly executes the detection until the magnetic marker 10 is detected (S102: NO). When the detection unit 12 receives an input indicating that the magnetic marker 10 has been detected from the front sensor unit 11 (S102: YES), the detection unit 12 is a time period for causing the rear sensor unit 11 to perform marker detection processing. A period is set (S103, period setting step).

  Specifically, as shown in FIG. 8, the detection unit 12 first calculates a required time δta obtained by dividing the sensor span S (m) by the vehicle speed (vehicle speed) V (m / second) measured by the vehicle speed sensor. The time t1, which is the time when the magnetic marker 10 is detected by the front sensor unit 11, is added. In this way, by adding the required time δta to the time t1, the time t2 when the rear sensor unit 11 can detect the magnetic marker 10 can be predicted. The detection unit 12 starts from the time (t2−δtb) obtained by subtracting the section time δtb obtained by dividing the reference distance 1 (m) by the vehicle speed V (m / second) from the time t2, and uses the section time δtb as the time. A time interval in which the time (t2 + δtb) added to t2 ends is set as the detection period. The reference distance can be appropriately changed in consideration of the detection range of the sensor unit 11 and the like.

  The detection unit 12 causes the rear sensor unit 11 to repeatedly execute the marker detection process within the detection period of FIG. 8 (S104: NO → S114, second detection step). The contents of this marker detection process are the same as the marker detection process by the front sensor unit 11 in step S101. When the detection period ends (S104: YES), the detection unit 12 determines whether or not the magnetic marker 10 has been detected according to whether or not the rear sensor unit 11 has detected the magnetic marker 10 (S105). Is determined and output (S106, S116).

  Following the detection of the magnetic marker 10 by the front sensor unit 11 (S102: YES), the detection unit 12 detects the magnetic marker 10 even in the rear sensor unit 11 in the detection period (FIG. 8). (S105: YES), the fact that the magnetic marker 10 has been detected is confirmed and output to the vehicle ECU or the like (S106). When the rear sensor unit 11 detects the magnetic marker 10, the process may proceed to step S106 without waiting for the end of the detection period.

  On the other hand, the magnetic marker 10 can be detected by the front sensor unit 11 (S102: YES), but the magnetic marker 10 cannot be detected by the rear sensor unit 11 in the detection period (FIG. 8). (S105: NO), as a final determination, the detection unit 12 determines and outputs that the magnetic marker 10 has not been detected (S116).

  According to the magnetic marker detection system 1 configured as described above, for example, even when the front sensor unit 11 erroneously detects the magnetic marker 10, no erroneous detection is immediately caused. This is because the detection of the magnetic marker 10 by the front sensor unit 11 only triggers the marker detection process by the rear sensor unit 11.

  In this magnetic marker detection system 1, the fact that the rear sensor unit 11 has detected the magnetic marker 10 within a detection period (predetermined period) based on the time point when the front sensor unit 11 detects the magnetic marker 10. This is a condition for confirming that the magnetic marker 10 has been detected. When this condition is satisfied, the determination that the magnetic marker 10 has been detected is finalized. Since the marker detection processing by the rear sensor unit 11 is executed only when the magnetic marker 10 is detected by the front sensor unit 11, the possibility of erroneous detection is reduced.

  As described above, the magnetic marker detection system 1 uses the plurality of sensor units 11 to perform the marker detection process while slightly shifting the timing in time. Then, when a plurality of sensor units 11 can detect the same magnetic marker 10, the determination that the magnetic marker 10 has been detected is confirmed. In this magnetic marker detection system 1, the plurality of sensor units 11 execute marker detection processing, respectively, thereby improving detection reliability.

  In this example, the configuration in which the front and rear sensor units 11 execute the marker detection process is illustrated. However, all the sensor signals of each magnetic sensor Cn are taken into the detection unit 12 and all processes are executed by the detection unit 12. It is also possible to adopt a configuration. During the operation of the magnetic marker detection system 1, either one of the front side sensor unit 11 and the rear sensor unit 11 alternatively executes marker detection processing. In the detection period, the rear sensor unit 11 executes the marker detection process, while in the other system operation periods, the front sensor unit 11 executes the marker detection process. While the magnetic marker detection system 1 includes two sensor units 11, the marker detection processing of the two sensor units 11 is not performed simultaneously. Therefore, it is possible to easily adopt a configuration in which all sensor signals of each magnetic sensor Cn are taken into the detection unit 12 and all processing is executed by the detection unit 12. If such a configuration is adopted, the scale of hardware can be suppressed and the cost can be suppressed.

  In the magnetic marker detection system 1, the length of the detection period (FIG. 8) in which the rear sensor unit 11 executes the marker detection process varies according to the vehicle speed. The length of the detection period is shorter as the vehicle speed is higher, and is longer as the vehicle speed is lower. By adopting such a configuration, the occurrence of false detection can be suppressed in advance by suppressing the proportion of time during which the magnetic marker 10 is not located in the detection range of the sensor unit 11 on the rear side in the detection period.

  The marker detection process may be always executed for the front and rear sensor units 11. In this case, when the front sensor unit 11 detects the magnetic marker 10, a predetermined period is set as in the detection period of FIG. 8, and the detection result of the rear sensor unit 11 in this predetermined period is used. It is advisable to finalize the final detection result. After the front sensor unit 11 detects the magnetic marker 10, when the rear sensor unit 11 detects the magnetic marker 10 within a predetermined period, the determination that the magnetic marker 10 has been detected may be confirmed.

  Note that the threshold value (see FIG. 6) indicating whether or not the detection is made may be different between the front sensor unit 11 and the rear sensor unit 11. For example, the threshold value of the front sensor unit 11 may be set loosely, while the threshold value of the rear sensor unit 11 may be set strictly. In this case, the detection failure of the magnetic marker 10 by the front sensor unit 11 can be suppressed, and the reliability of detection of the magnetic marker by the rear sensor unit 11 can be ensured.

  The first lateral deviation amount when the front sensor unit 11 detects the magnetic marker 10 and the second lateral deviation amount when the rear sensor unit 11 detects the magnetic marker 10 are input to the detection unit 12. Also good. The detection unit 12 may use a fluctuation amount that is a difference between two lateral deviation amounts as one of index values for deterministically determining whether or not the magnetic marker 10 has been detected. For example, if the fluctuation amount is excessive with respect to the sensor span S (FIG. 2), it is not appropriate to determine that the magnetic marker 10 detected by the front sensor unit 11 and the rear sensor unit 11 is the same. It can be determined that the reliability of the detection result is low or the magnetic marker 10 is not detected.

  In this example, the sensor units 11 are provided at two locations in the front-rear direction of the vehicle. Instead of this, the sensor units 11 may be provided at three or more locations in the longitudinal direction of the vehicle. The magnetic marker detection method of this example can be applied to any combination of two different positions in the front-rear direction, and a plurality of combinations of two different positions may be combined. For example, in the case of three sensor units at the front, center, and back in the front-rear direction, the magnetic marker detection method can be applied to the front-back combination, front-center combination, and center-back combination. And it is also possible to determine whether or not to detect by combining three results derived from the three types of combinations. For example, it may be determined that detection is made when all three results are detection, or it may be determined whether or not detection is made by majority vote.

  In addition to the terrestrial magnetism, the sensor unit 11 is caused by common noise, which is magnetic noise that is nearly uniform, due to a large magnetic source such as an iron bridge or another vehicle. doing. Such common noise is highly likely to act uniformly on each magnetic sensor Cn of the sensor unit 11. Therefore, it is also possible to detect the magnetic marker 10 using the difference value of the magnetic measurement values of the magnetic sensors Cn arranged in the vehicle width direction. With this difference value representing the magnetic gradient in the vehicle width direction, common noise acting uniformly on each magnetic sensor Cn is effectively suppressed. As shown in FIG. 9, the distribution waveform of the difference value is a waveform of a staggered two peaks in which a zero cross occurs corresponding to the position of the magnetic marker 10 in the vehicle width direction, and the positive and negative are opposite on both sides of the zero cross.

  When the vehicle 5 to which the sensor unit 11 is attached passes through the magnetic marker 10, the amplitude of the distribution waveform of the lid mountain gradually increases as the vehicle 5 approaches the magnetic marker 10, and the maximum amplitude is directly above the magnetic marker 10. (Period of p4). Thereafter, as the vehicle 5 moves away from the magnetic marker 10, the amplitude of the distribution waveform of the top mountain gradually decreases. In order to detect the magnetic marker 10 using the distribution waveform of the difference value as described above, for example, threshold judgment regarding the amplitude of the positive and negative lid peaks on both sides of the zero cross may be applied. The position of the zero cross may be specified as the lateral deviation amount. It is also effective to specify the position of the zero cross with high accuracy using linear approximation or curve approximation.

  Instead of the front sensor unit 11 including 15 magnetic sensors Cn, a sensor unit including one magnetic sensor may be employed. It is also possible to input the magnetic measurement value of the magnetic sensor to the detection unit 12 and execute the marker detection process by the detection unit 12. As described above, the front magnetic sensor may be used only for detecting the presence or absence of the magnetic marker 10 and the rear sensor unit 11 may detect the presence or absence of the magnetic marker 10 and the amount of lateral deviation. In this case, the system configuration can be simplified and the cost can be suppressed. The rear magnetic sensor may be used only for detecting the presence / absence of the magnetic marker 10 and the front sensor unit 11 may detect the presence / absence of the magnetic marker 10 and the amount of lateral deviation.

  In the marker detection process by the front sensor unit 11 or the rear sensor unit 11, a difference in magnetic measurement value is calculated between the magnetic sensor of the front sensor unit 11 and the magnetic sensor of the rear sensor unit 11, and this It is also possible to detect the magnetic marker 10 using the calculated value. According to this difference calculation, a difference magnetic component obtained by subtracting the magnetic component detected by the front magnetic sensor from the magnetic component detected by the rear magnetic sensor can be generated, which is effective in suppressing the common noise and the like. In the difference calculation, the difference may be obtained between magnetic sensors having the same position in the vehicle width direction.

In this example, the magnetic sensor Cn having sensitivity in the vertical direction is employed. However, a magnetic sensor having sensitivity in the traveling direction may be used, or a magnetic sensor having sensitivity in the vehicle width direction may be used. Further, for example, a magnetic sensor having sensitivity in the biaxial direction of the vehicle width direction and the traveling direction, the biaxial direction of the vehicle width direction and the vertical direction, or the biaxial direction of the traveling direction and the vertical direction may be employed. A magnetic sensor having sensitivity in the three axial directions of the vehicle width direction, the traveling direction, and the vertical direction may be employed. If a magnetic sensor having sensitivity in a plurality of axial directions is used, the magnetic action direction can be measured together with the magnitude of the magnetism, and a magnetic vector can be generated. It is also possible to distinguish between the magnetism of the magnetic marker 10 and the disturbance magnetism using the difference of the magnetic vectors and the rate of change in the traveling direction of the difference.
In this example, a magnetic marker of a ferrite plastic magnet is illustrated, but a magnetic marker of a ferrite rubber magnet may be used.

(Example 2)
This example is an example of a magnetic marker detection system in which the control method of the sensor unit 11 is changed based on the configuration of the first embodiment. The contents will be described with reference to FIG. 10 and FIG. 11 as well as the block diagram of FIG.

  The operation of the magnetic marker detection system 1 will be described with reference to the flowchart of FIG. The detection unit 12 causes the front sensor unit 11 and the rear sensor unit 11 to execute marker detection processing in parallel (S201, S211). The detection unit 12 captures the detection result of each sensor unit 11 (S202), and for the detection result of the front sensor unit 11, the detection result over a preset storage period (within several seconds) is illustrated as time-series data. Temporary storage in the storage area not to be performed (S203).

  When a magnetic marker is detected by the rear sensor unit 11 (S204: YES), the detection unit 12 has a history of detection results corresponding to a predetermined period of time-series data of detection results of the front sensor unit 11. (S205). The predetermined period of the reference target is calculated based on the time when the rear sensor unit 11 detects the magnetic marker as a reference, and the front sensor unit 11 may detect the same magnetic marker. The period to include is set.

  Specifically, as shown in FIG. 11, the detection unit 12 uses the vehicle speed (vehicle speed) V (m / second) measured by the vehicle speed sensor to divide the required time δta by the above time δta. It subtracts from time t2, which is the time of detection of the magnetic marker by the sensor unit 11 on the side. In this way, by subtracting the required time δta from the time t2, it is possible to calculate the time t1 when there is a possibility that the front sensor unit 11 can detect the magnetic marker. Then, the detection unit 12 starts from the time (t1−δtb) obtained by subtracting the section time δtb obtained by dividing the reference distance 1 (m) by the vehicle speed V (m / second) from the time t1, and uses the section time δtb as the time. A time interval in which the time (t1 + δtb) added to t1 ends is set as the predetermined period of the reference object.

  The detection unit 12 refers to the detection result within the predetermined period in the time-series data of the detection result of the front sensor unit 11, and checks whether there is a detection result indicating that the magnetic marker has been detected. If there is a detection result indicating that the magnetic marker has been detected (S206: YES), the magnetic marker detected by the rear sensor unit 11 has also been detected by the front sensor unit 11. The determination that the marker has been detected is confirmed (S207).

  On the other hand, when the detection unit 12 does not include a result indicating that the magnetic marker has been detected in the detection results of the predetermined period in the time-series data of the detection result of the front sensor unit 11 (S206). : NO), the determination that the magnetic marker is not detected is fixed (S217).

The storage period for temporarily storing the detection result of the front sensor unit 11 includes the time required to pass the distance obtained by adding the reference distance to the distance of about 4 to 5 m that is the length of the vehicle. Any period is acceptable. Of course, since this time required for passage varies depending on the vehicle speed, the storage period may be shortened as the vehicle speed increases.
Other configurations and operational effects are the same as those in the first embodiment.

  As described above, specific examples of the present invention have been described in detail as in the embodiments. However, these specific examples merely disclose an example of the technology included in the scope of claims. Needless to say, the scope of the claims should not be construed as limited by the configuration, numerical values, or the like of the specific examples. The scope of the claims includes techniques obtained by variously modifying, changing, or appropriately combining the above specific examples using known techniques and knowledge of those skilled in the art.

DESCRIPTION OF SYMBOLS 1 Magnetic marker detection system 10 Magnetic marker 100 Lane 11 Sensor unit (marker detection means)
110 detection processing circuit 12 detection unit (determination means, period setting means)
21 MI element 5 Vehicle

Claims (8)

A magnetic marker detection system for detecting a magnetic marker disposed on a travel path using marker detection means provided at least at two locations separated in the front-rear direction of the vehicle,
Determination to determine whether or not a magnetic marker has been detected based on at least one of the detection result of the magnetic marker by the front marker detection means and the detection result of the magnetic marker by the rear marker detection means Having means,
In the determination means, the other marker detection means detects the same magnetic marker within a predetermined period based on the time point when one of the front and rear marker detection means detects the magnetic marker, A magnetic marker detection system that is set as a condition for determining a determination that a magnetic marker has been detected.   2. The time period including a time point at which the rear marker detection unit is predicted to detect the same magnetic marker when the front marker detection unit detects a magnetic marker, according to claim 1, as the predetermined period. A magnetic marker detection system having period setting means for setting.   3. The magnetic marker detection system according to claim 2, wherein the rear marker detection means executes a magnetic marker detection process in the predetermined period. In any one of Claim 2 or 3, any one of the said marker detection means of the said front side and a back side performs the detection process of a magnetic marker alternatively,
A magnetic marker detection system in which the rear marker detection means performs detection processing during the predetermined period, while the front marker detection means performs detection processing during other operating periods.   5. The magnetic marker detection system according to claim 1, wherein a length of the predetermined period is different according to a vehicle speed that is a speed of the vehicle, and the predetermined period is shorter as the vehicle speed is higher. In any one of Claims 1-5, the said marker detection means can detect the lateral deviation | shift amount of the vehicle facing a magnetic marker,
The index value for the determination means to confirm the determination includes a difference between the first lateral deviation amount detected by the front marker detection means and the second lateral deviation amount detected by the rear marker detection means. Magnetic marker detection system that contains the amount of variation. A magnetic marker detection method for detecting a magnetic marker disposed on a travel path using marker detection means provided at at least two locations separated in the longitudinal direction of the vehicle,
A first detection step of performing magnetic marker detection processing by the front marker detection means;
When a magnetic marker is detected by the front marker detection means, a time point at which the rear marker detection means can detect the same magnetic marker is predicted based on the time point of the detection, and a predetermined period including the time point at which the detection is possible is determined. A period setting step to be set;
A magnetic marker detection method comprising: a second detection step of executing a magnetic marker detection process by the rear marker detection means in a predetermined period set in the period setting step.   8. The magnetic marker detection method according to claim 7, wherein the first detection step is repeatedly executed until a magnetic marker is detected by the front marker detection means.

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